Hi,
I've been working on this myself, and I can answer a few questions for you.
The SRT/10 units are Dodge. So you can get "Dodge to Universal" adapter plugs from places like Circuit City or online. If you plan on buying an aftermarket unit and wiring it into the existing system, you'll need a Line-Output Convertor, also known as a high-level-to-low-level convertor. This is because aftermarket units have built-in amps, but your Viper has it's own Amp. If you double-amp the signal you can damage the factory amp and/or blow out speakers.
The best source I've found so far for these is here:
ANTOnline.com
Your aftermarket head unit will come with a pigtail harness - wire it into the converter, wire the converter into the dodge-to-universal adapter, get an adapter trim piece for the aftermarket stereo (also available at Circuit City or online) and you should be set.
Jeff